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    <title>tf2des</title>
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    <center>Scilab Function</center>
    <div align="right">Last update : April 1993</div>
    <p>
      <b>tf2des</b> -  transfer function to descriptor</p>
    <h3>
      <font color="blue">Calling Sequence</font>
    </h3>
    <dl>
      <dd>
        <tt>S=tf2des(G)  </tt>
      </dd>
      <dd>
        <tt>S=tf2des(G,flag)  </tt>
      </dd>
    </dl>
    <h3>
      <font color="blue">Parameters</font>
    </h3>
    <ul>
      <li>
        <tt>
          <b>G</b>
        </tt>: linear system (<tt>
          <b>syslin</b>
        </tt> list) with possibly polynomial <tt>
          <b>D</b>
        </tt> matrix</li>
      <li>
        <tt>
          <b>flag</b>
        </tt>: character string <tt>
          <b>"withD"</b>
        </tt>
      </li>
      <li>
        <tt>
          <b>S</b>
        </tt>: list</li>
    </ul>
    <h3>
      <font color="blue">Description</font>
    </h3>
    <p>
    Transfer function to descriptor form: <tt>
        <b>S=list('d',A,B,C,D,E)</b>
      </tt>
    </p>
    <pre>

  E*xdot = A*x+B*u
  y = C*x + D*u
   
    </pre>
    <p>
    Note that <tt>
        <b>D=0</b>
      </tt> if the optional parameter flag=<tt>
        <b>"withD"</b>
      </tt> is not
    given. Otherwise a maximal rank <tt>
        <b>D</b>
      </tt> matrix is returned in the fifth
    entry of the list <tt>
        <b>S</b>
      </tt>
    </p>
    <h3>
      <font color="blue">Examples</font>
    </h3>
    <pre>

s=poly(0,'s');
G=[1/(s-1),s;1,2/s^3];
S1=tf2des(G);des2tf(S1)
S2=tf2des(G,"withD");des2tf(S2)
 
  </pre>
    <h3>
      <font color="blue">See Also</font>
    </h3>
    <p>
      <a href="../polynomials/pol2des.htm">
        <tt>
          <b>pol2des</b>
        </tt>
      </a>,&nbsp;&nbsp;<a href="../control/tf2ss.htm">
        <tt>
          <b>tf2ss</b>
        </tt>
      </a>,&nbsp;&nbsp;<a href="../control/ss2des.htm">
        <tt>
          <b>ss2des</b>
        </tt>
      </a>,&nbsp;&nbsp;<a href="../control/des2tf.htm">
        <tt>
          <b>des2tf</b>
        </tt>
      </a>,&nbsp;&nbsp;</p>
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